1. Field of the Invention
The present invention generally relates to a focusing module for small-sized electronic or digital imaging device, and in particular to a focusing device that operates on the movement of resilient membrane induced by magnetic forces to effect fine adjustment of focusing.
2. The Related Arts
Digital or electronic imaging devices, such as mobile phones, digital cameras, web cameras, pin-hole cameras, are widely used in a variety of applications. These imaging device effect focusing operation in digital focusing or optic focusing manner. The digital focusing is effected by data processing preformed by a digital image integrated circuit (IC). The advantage of the digital focusing is the reduction of number of optic elements and thus costs of manufacturing, as well as reduced overall size. However, digital focusing surfers image display delay and blurring and distortion of image. This is due to the data processing is very time consuming, and the result of processing often makes the image distorted, making it impossible to show the true image.
As to the optic focusing, an example is shown in Taiwan Utility Model Publication No. 588551, which illustrates an automatic focusing device, in which a movable lens holder and a casing of a digital camera engage each other with threadings. Electro-magnetic driving means having a construction similar to a motor is employed to rotate the lens for axially displacing the lens to effect focusing operation. The focusing operation of the conventional devices requires continuously rotating the lens, which may causes the lens to inadvertently separate from the holder or induces error of focusing due to the vibration or shaking of the lens caused by rotation thereof. Further, the threading and electromagnetic driving means cannot be modularized, which makes the focusing device very bulky and requiring a large-sized casing to accommodate the parts. Consequently, manufacturing process of digital camera gets complicated and manufacturing costs increased.
In addition, inertial force of the bulky and often heavy parts of the optic focusing device makes it difficult to control the operation thereof and delays the time interval that is required to move the lens to a desired position. The vibration or shaking caused by rotation of the lens ad the mechanical noise and vibration caused by the threading engagement also impose undesired error to the final result of image display, which is often overcome by employing additional vibration-absorbing device. This further increases the costs.
The present invention is made to overcome the drawbacks of the conventional focusing devices.